1. Field
This disclosure relates generally to a control channel and, more specifically, to techniques for extracting a control channel from a received signal in a wireless communication system.
2. Related Art
Wireless networks that employ third-generation partnership project long-term evolution (3GPP-LTE) compliant architectures are required to employ uplink reference signals (RSs) for uplink carrier-to-interference and noise ratio (CINR) estimation, which is used by the networks to schedule uplink transmissions for user equipment (subscriber stations (SSs)). Respective sequences of the RSs are used to uniquely identify an SS and, when transmitted from the SS to a serving base station (BS), may be used by the serving BS in channel characterization. In general, a scheduler associated with one or more serving BSs utilizes information derived from channel characterization to determine channel allocation for the SSs. The channel allocation, e.g., uplink and downlink assignments, have then been provided to the SSs over a downlink shared control channel, which typically includes one or more control channel symbols. The one or more control channel symbols may be transmitted by the serving BS at a beginning of a downlink frame (or subframe). Typically, upon receiving the one or more control channels symbols, each of the SSs searches the one or more control channel symbols to determine an associated uplink and downlink assignment.
Data is often transmitted with error correction bits that allow a receiver to correct a certain number of errors that occur during transmission. However, when a burst error occurs, more errors may be produced in a single codeword than can be corrected. For example, a burst error may overwrite multiple bits in a row and, as such, may overwhelm a typical error correction scheme that expects errors to be uniformly distributed. In this case, a received codeword cannot be correctly decoded. To reduce the effect of burst errors, bits of a number of codewords may be interleaved before being transmitted. When interleaving is employed, a burst error may be limited to only affecting a correctable number of bits in each codeword, such that a decoder can correctly decode the codewords. In general, interleaving is popular as it usually provides a less complex and lower cost approach to handling burst errors than directly increasing a complexity of an error correction scheme. However, interleaving techniques usually increase latency as an entire interleaved block must be received before received data can be deinterleaved and decoded.
A number of different data deinterleaving approaches are known. For example, U.S. Pat. No. 6,965,557 (assigned to LG Electronics Inc.) proposes specific logic to increase data access speed by improving addressing and access operation of an interleaved memory in a code division multiple access (CDMA) system. As another example, U.S. Pat. No. 6,748,561 (assigned to Sony Corporation) discloses reading and writing symbols in alternate sequences during interleaving/deinterleaving to reduce memory requirements (two buffers for each frame of symbols). In general, the approach multiplexes interleaving procedures for two consecutive frames and employs two buffers for each frame of symbols. As yet another example, U.S. Pat. No. 7,386,766 (assigned to Thomson Licensing), which is directed to a turbo encoder/decoder in a wideband-code division multiple access (W-CDMA) system, discloses alternating two frames to save memory, similar to U.S. Pat. No. 6,748,561.
In long-term evolution (LTE) compliant wireless communication systems, LTE physical downlink control channel (PDCCH) deinterleaving is an implementation issue that is vendor specific. A known deinterleaving approach for an LTE compliant wireless communication system has proposed reordering data samples in three steps using three read and three write operations of an entire control channel region of a memory.